TENSION CONTROL DEVICE FOR HOT ROLLING AND TENSION CONTROL METHOD FOR SAME
TECHNICAL FIELD
The present invention relates to a tension control device for hot rolling and a control method for the same, and more particularly, a tension control device and a tension control method for the same which are suitable for reducing interaction between a tension control for a strip between stands and a looper height control to acquire stable tension and looper height.
BACKGROUND ART
Tension of a strip between stands, each of which has rolling rolls for feeding the strip in hot rolling, can be controlled by changing a rolling condition of the strip with a roll speed difference (a difference between main drives driving the respective rolls) between forward and backward stands in a rolling step and by changing a looper height of a looper which lifts up the strip to stabilize feeding thereof.
At the same time, when a rolling condition of the strip is changed with a roll speed difference to change tension of the strip, a load applied to the strip changes due to the change in the strip tension, so that a looper height is changed.
Conversely, when a looper height is changed and a lift-up condition of the strip is changed to change strip tension, a disturbance acts on a drive speed of the strip due to a change in a feeding load of the strip. Thus, a tension control for a strip and a looper height control between stands are mutually-affecting interactive systems.
As conventional methods of controlling tension in hot rolling using a looper, for example, JPH09-192716A and JPH05-337529A disclose a control method performed by a control system that comprises a two-input/two-output system in which a speed of an electric motor for driving rolling rolls and a speed of a looper electric motor are used as inputs, and
tension of a strip and an amount acquired by multiplying the tension by a weighting parameter and added to a looper angle are used as control amounts. The method calculates a speed instruction value for each electric motor based on a control gain calculated out using a hot rolling device process model of a control target.
In addition, JPH05-337529A discloses a method of causing strip tension and a looper height both output by a control system to be mutually non-interactive using a control gain.
DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention
In the meantime, according to the methods disclosed in those foregoing literatures, since both looper height and strip tension are changed by controlling a looper height, as a change in the looper height originating from a change in the changed strip tension acts on a looper height control, a looper height may be moved unnecessarily.
Moreover, since a control system directly employs a two-input/two-output • multi-variable system, adjustment of the control system needs a large amount of knowledge, so that prospects for the adjustment may be difficult.
The present invention has been made in view of the foregoing circumstance, it is an object of the present invention to provide a tension control device for hot rolling and a tension control method for the same which can cause a tension control for a rolling target like a strip and a looper height control to be mutually non-interactive with a simple method, based on separating the tension control for the rolling target like the strip and the looper control in hot rolling into two control systems each of which is a one-input/one-output system with good prospects. Means for Solving the Problem
To achieve the object, a tension control device for hot rolling according to the first aspect of the present invention controls a hot rolling mill having plural rolling stands and a
looper between the plural rolling stands and controls tension of a rolling target like a strip to a desired value, the rolling target is rolled continuously by work rolls of the individual rolling stands, and the tension control device comprises: tension control unit for controlling the tension of the rolling target to a desired value by controlling a work roll rotation speed of each rolling stand; speed control unit for calculating, from an output by the tension control unit, a speed instruction for a drive device which drives the work rolls, the speed instruction being for controlling the work roll rotation speed; loading torque observing unit for acquiring an actual value of backward tension which is tension of the rolling target entering into the rolling stand, an actual value of forward tension which is tension of the rolling target ejected from the rolling stand, and an actual value of a rolling load of the rolling stand from the hot rolling mill, and for estimating a loading torque of the drive device; looper height control unit for calculating a height instruction for a looper drive device which controls a height of the looper; and looper supporting torque estimating unit for acquiring an actual value of the forward tension and an actual value of a height of the looper from the hot rolling mill, and for estimating a torque necessary for the looper to support the rolling target, and wherein:
a control instruction which is a value acquired by computing an output that is a speed instruction calculated by the speed control unit and an output that is a loading torque estimated by the loading torque observing unit is output to the drive device; and a control instruction which is a value acquired by computing an output that is a height instruction calculated by the looper height control unit and an output that is a torque estimated by the looper supporting torque estimating unit is output to the looper drive device.
A tension control device for hot rolling according to the second aspect of the present invention controls a hot rolling mill having plural rolling stands and a looper between the plural rolling stands and controls tension of a rolling target like a strip to a desired value, the rolling target being rolled continuously by work rolls of the individual rolling stands, and the tension control device comprises: tension control unit for controlling the tension of the rolling
target to a desired value by controlling a work roll rotation speed of each rolling stand; speed control unit for calculating, from an output by the tension control unit, a speed instruction for a drive device which drives the work rolls, the speed instruction being for controlling the work roll rotation speed; loading torque observing unit for acquiring an actual value of backward tension which is tension of the rolling target entering into the rolling stand and an actual value of a rolling load of the rolling stand from the hot rolling mill, and for estimating a loading torque of the drive device using a target value of forward tension which is tension of the rolling target ejected from the rolling stand; looper height control unit for calculating a height instruction for a looper drive device which controls a height of the looper; and looper supporting torque estimating unit for acquiring an actual value of the forward tension and an actual value of a height of the looper from the hot rolling mill, and for estimating a torque necessary for the looper to support the rolling target, and wherein: a control instruction which is a value acquired by computing an output that is a speed instruction calculated by the speed control unit and an output that is a loading torque estimated by the loading torque observing i unit is output to the drive device; and a control instruction which is a value acquired by computing an output that is a height instruction calculated by the looper height control unit and an output that is a torque estimated by the looper supporting torque estimating unit is output to the looper drive device.
A tension control method for hot rolling according to the third aspect of the present invention comprises plural rolling stands and a looper provided between the rolling stands to support a rolling target like a strip to stabilize a rolling process by a supporting height, and controls tension of the rolling target to a desired value, the rolling target being rolled continuously by work rolls of individual rolling stands, and the method comprises steps of: calculating a rotation speed of a drive device which drives the work rolls in order to control the tension of the rolling target to a desired value; calculating a speed instruction value for the drive device corresponding to the rotation speed of the drive device; acquiring an actual value
of backward tension which is tension of the rolling target entering into the rolling stand, an actual value of forward tension which is tension of the rolling target ejected from the rolling stand and an actual value of a rolling load of the rolling stand, and estimating a loading torque of the drive device which drives the work rolls; outputting a control instruction which is a value acquired by computing a speed instruction value for the drive device and a loading torque of the drive device to the drive device; calculating a height instruction value for a looper drive device which controls a height of the looper to a desired value; acquiring an actual value of the forward tension and an actual value of a height of the looper and estimating a supporting torque necessary for the looper drive device to support the rolling target; and outputting a control instruction which is a value acquired by computing a supporting torque for the looper drive device and a height instruction value for the looper drive device to the looper drive device.
A tension control method for hot rolling according to the fourth aspect of the present invention comprises plural rolling stands and a looper provided between the rolling stands to support a rolling target like a strip to stabilize a rolling process by a supporting height, and controls tension of the rolling target to a desired value, the rolling target being rolled continuously by work rolls of individual rolling stands, and the method comprises steps of: calculating a rotation speed of a drive device which drives the work rolls in order to control the tension of the rolling target to a desired value; calculating a speed instruction value for the drive device corresponding to the rotation speed of the drive device; acquiring an actual value of backward tension which is tension of the rolling target entering into the rolling stand and an actual value of a rolling load of the rolling stand, and estimating a loading torque of the drive device which drives the work rolls using a target value of forward tension which is tension of the rolling target ejected from the rolling stand; outputting a control instruction which is a value acquired by computing a speed instruction value for the drive device and a loading torque of the drive device to the drive device; calculating a height instruction value
for a looper drive device which controls a height of the looper to a desired value; acquiring an actual value of the forward tension and an actual value of a height of the looper and estimating a supporting torque necessary for the looper drive device to support the rolling target; and outputting a control instruction which is a value acquired by computing a supporting torque for the looper drive device and a height instruction value for the looper drive device to the looper drive device.
According to the present invention, it becomes possible to realize a tension control device for hot rolling and a tension control method for the same which can cause a tension control for a rolling target like a strip and a looper height control to be mutually non-interactive with a simple method.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a conceptual diagram showing a structure of a control system having a tension control device according to a first embodiment of the present invention;
FIG. 2 is a diagram showing a configuration of tension target value storing means according to the first embodiment;
FIG. 3 is a diagram showing a process executed by loading torque estimating means according to the first embodiment;
FIG. 4 is a diagram showing an example where a strip is rolled by work rolls according to the first embodiment;
FIG. 5 is a diagram showing a structure of looper-height-instruction generating means according to the first embodiment;
FIG. 6 is a diagram showing a process of looper supporting torque estimating means according to the first embodiment;
FIG. 7 is a diagram showing an example where a strip being rolled by stands is supported by a looper arm according to the first embodiment;
FIG. 8 is a diagram showing a structure of a control system according to a second embodiment of the present invention; and
FIG. 9 is a diagram showing a flow of a process executed by loading torque observing means according to the second embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be explained with reference to the accompanying drawings. «First Embodiment»
FIG. 1 is a conceptual diagram showing a structure of a control system S having a tension control device 150 according to a first embodiment of the present invention.
The tension control device 150 shown in FIG 1 according to the first embodiment can stabilize a tension control for a material at a finishing stand in hot rolling in which the material like a heated strip 103 is fed in between two rotating work rolls 104 to change a cross section of the material to a predetermined shape while decreasing the cross section. The tension control device 150 can improve stability at the time of rolling the material and a feeding performance, resulting in achievement of a highly-precise material thickness. Moreover, the tension control device 150 can reduce width shrinkage deviation inherent to a tension change by stabilizing tension of the material at the time of rolling, thereby improving a width precision. Overall Structure of Control System S having Tension Control Device 150>
The control system S shown in FIG. 1 according to the first embodiment has a hot rolling device 100 which is a control target performing hot rolling on a material like a strip 103, and the tension control device 150 which controls the hot rolling device 100 to control tension of the material at the time of hot rolling.
Note that an explanation below will be given of a case where a material subjected to hot rolling is the strip 103.
The tension control device 150 receives various signals, such as a detecting signal of tension of the strip 103 at the time of hot rolling, a detecting signal of a height of a support unit 112a of a looper 110 and a detecting signal of a rotation of a drive device conveying the strip 103, from the control-target hot rolling device 100, and outputs a control signal to the control-target hot rolling device 100 in accordance with received signals.
First, an explanation will be given of a structure of the hot rolling device 100 which is the control target of the tension control device 150.
As shown in FIG 1, the hot rolling device 100 has plural stands 101, 120 each for rolling the rolling-target strip 103, and has the looper 110 provided between the stand 101 and the stand 120 to lift up the rolling-target strip 103 in order to adjust tension thereof, and to stabilize feeding of the strip 103.
For example, stands 101 120 each has a four-stage mill structure having the upper and bottom work rolls 104 directly sandwiching the strip 103 in the vertical direction and actually rolling the strip 103, and upper and bottom backup rolls 105 supporting the respective upper and bottom work rolls 104.
The upper and bottom work rolls 104 in the stand 101 are individually driven by a drive device 109 having a motor or the like which performs direct driving.
Likewise, the upper and bottom work rolls 104 in the delivery-side stand 120 are individually driven by a drive device 121 having a motor or the like which performs direct driving.
It is not illustrated in FIG 1, but the stands 101, 120 each also has a drive device for driving the upper and bottom backup rolls 105.

The looper 110 shown in FIG 1 is a device which has a function of stabilizing tension of the strip 103 and feeding thereof by lifting up and supporting the strip 103 that is the rolling target conveyed between the stand 101 and the stand 120. The looper 110 is generally i attached between individual stands 101, 120.
The looper 110 has, for example, a looper arm 112 which actually lifts up and supports the fed rolling-target strip 103 and a looper cylinder 111 like a hydraulic cylinder which rotates the looper arm 112 in a direction of an arrow a 12.
As a looper drive device 108 controls the looper cylinder 111 to elongate and contract, the looper 110 rotates the looper arm 112 in the direction of the arrow a 12, and the support unit 112a of a freely-rotatable roller of the looper arm 112 which actually supports the rolling-target strip 103 is subjected to a height control.
The height of the supporting member 112a which supports the rolling-target strip 103 in the looper arm 112 is detected by a height meter 114.
Plural stands are provided further in front and back of each stand 101, 120 of the hot rolling device 100 shown in FIG 1, i.e., in the entry side and the delivery side of the conveyed direction (a direction of an arrow all in FIG 1) of the strip 103 in such a manner as to sandwich the looper 110 likewise FIG 1. Note that six to seven stands are generally arranged in an ordinary finishing mill.
As shown in FIG 1, the hot rolling device 100 is a tandem mill which successively rolls the rolling-target strip 103 using the plural stands 101, 120 while upwardly supporting the strip 103 by the looper arm 112.
In the hot rolling device 100, as the strip 103 is moved in the direction of the arrow ocl 1 in FIG 1 from the stand 101 to the stand 120 with the looper 110 being present therebetween, the strip 103 is pressed by the work rolls 104, 104 of the stands 101, 120 and rolled so as to be
gradually thin.
At the time of rolling, in the strip 103 which is present between the stand 101 and the stand 120, tension which pulls up the strip 103 in a lengthwise direction (horizontal direction of FIG 1) is generated due to a driving speed difference of the work rolls 104 of the respective entry-side and delivery-side stands 101, 120, a height of the looper arm 112 and the like.
Regarding the individual stands 101, 120, let us suppose that tension of the strip 103 at an entry side (left side of FIG 1) is "backward tension tb, and tension of the strip 103 at a delivery side (right side of FIG. 1) is forward tension tf. For example, tension of the strip 103 entering into the stand 101 is backward tension tb, and tension of the strip 103 ejected from the stand 101 is frontward tension tf.
Tension of the strip 103 which is present between the stand 101 and the stand 120 shown in FIG 1, i.e., frontward tension tf of the strip 103 ejected from the stand 101 is measured by a tension meter 113 attached to the looper arm 112. Meanwhile, backward tension tb of the strip 103 entering into the stand 101 is measured by a tension meter 132.
A rolling load applied to the strip 103 at each stand 101, 120 is detected by a load cell (not shown) attached to a rolling device of the stands 101, 120. The load cell detects a total rolling load. Alternatively, a rolling load of the strip 103 at each stand 101, 120 can be acquired by loading torque observing means 155 which acquires a rolling load distribution through well-known various equations, converts such a distribution into a rolling load per unit length, inputs the rolling load per unit into a calculation model, and acquires a rolling load through a method to be discussed later based on equilibrium of force at each stand 101, 120.
Regarding a speed (velocity) of the conveyed strip 103, a speed meter is provided to directly measure such a speed.
Next, an explanation will be given of a structure of the tension control device 150 shown
in FIG 1.
The tension control device 150 which controls tension of the strip 103 rolled by the hot rolling device 100 uses a PLC (Programmable Logic Controller).
First, a brief explanation will be given of a whole structure of the tension control device 150, and then an operation of each unit will be explained in detail.
Portions of the tension control device 150 surrounded by dashed lines in FIG. 1 control the stand 101 and the looper 110, and the tension control device 150 has the same function for successive another stand 120 and looper. An explanation will be given of the portions relating to the stand 101 and the looper 110 shown in FIG. 1.
Actual data gathering means 160 acquires actual data on the hot rolling device 100 in operation, such as a rolling load between the work rolls 104 of the stand 101, forward tension tf, backward tension tb, a height of the supporting member 112a of the looper arm 112, and a speed (velocity) of the strip 103, from the control-target hot rolling device 100.
The drive device 109 driving the upper and bottom work rolls 104 of the stand 101 in the hot rolling device 100 in FIG 1 is controlled in accordance with a tension instruction.
That is, tension control means 152 is activated in such a way that an actual value of the forward tension tf matches a tension instruction tf* stored in tension target value storing means 151, and then speed control means 154 performs a speed control on the drive of the strip 103 in accordance with an output AV* of the tension control means 152, and finally, a current instruction value for driving the drive device 109 is calculated, then a current instruction value is output to the drive device 109 after an output of the loading torque observing means 155 is added.
Note that the loading torque observing means 155 is a feed-forward compensator which causes a tension control to be non-interactive with a looper control system 150B (see FIG 1) to be discussed later.
The looper drive device 108 which activates the looper 110 is controlled in accordance with a looper height instruction output by looper height control means 157, i.e., a height instruction for the supporting member 112a of the looper arm 112. That is, the looper height control means 157 is activated in such a way that an actual value of a looper height (a height of the supporting member 112a of the looper arm 112) 9 matches a looper height instruction value (height instruction value of the supporting member 112a of the looper arm 112) 9*, and finally, a current instruction for driving the looper drive device 108 is calculated, then a current instruction value is output to the looper drive device 108 after an output by looper supporting torque observing means 158 is added. The looper height instruction value 9* is generated by looper height instruction generating means 156 in accordance with a length L of the strip 103 which has passed through the looper 110.
Note that the looper supporting torque estimating means 158 is a feed-forward compensator which causes a looper height control to be non-interactive with a tension control system 150A.
As explained above, in the control system S of the first embodiment, tension is controlled by a drive speed in the tension control system 150A, while a looper height is controlled by a looper height control in the looper control system 150B. Operation of Each Unit of Tension Control Device 150>
Next, an operation of each unit of the tension control device 150 will be explained in detail.

FIG. 2 is a diagram showing a configuration of the tension target value storing means 151.
In the tension target value storing means 151 shown in FIG 2, a tension instruction value 15Id which is forward tension tf applied to the strip 103 between individual stands is
stratified for a steel grade 151a, a strip thickness 151b and a strip width 151c, and an appropriate tension instruction value 15 Id for hot rolling is acquired beforehand for each condition and stored.
It is indicated that a tension instruction value 15 Id for tension to be applied to the strip 103 is 1.5 kg/mm2 (tension per unit area of a cross section of the strip 103) when a steel grade 151a is SS400, a strip thickness 151b is 2.0 to 3.0 mm and a strip width 151c is 900 mm.
The strip thickness 151b of the strip 103 between individual stands 101, 120 is uniquely determined based on a rolling schedule in the hot rolling device 100, then a tension instruction value 15Id is determined based on the steel grade 151a, the strip width 151c and the determined strip thickness 151b.
As stratified conditions other than the stratified conditions exemplified in the tension target value storing means 151 shown in FIG 2, a moving speed of the strip 103 and conditions for individual stands 101, 120 can be added.
As explained above, the stratified conditions for determining the tension instruction value 15 Id stored in the tension target value storing means 151 are not limited to the steel grade 151a, the strip thickness 151b and the strip width 151c.
If the tension instruction value 15 Id determined based on the steel grade 151a, the strip thickness 151b and the strip width 151c of the strip 103 to be rolled stored in the tension target value storing means 151 is a forward tension instruction value tf*, a difference Atf between the forward tension instruction value tf stored in the tension target value storing means 151 and a detected value of forward tension tf detected by the tension meter 113 shown in FIG 1 is input into the tension control means 152 shown in FIG 1. The tension control means 152 calculates a rotation speed input V* to be given to the speed control means 154.
If the rotation speed input V* is an instruction for a rotation speed and the drive device 109 driving the work rolls 104 is a motor, a unit of the rotation speed input V* is then rpm
(revolutions per minute) or mpm (meter per minute).
The rotation speed input V* can be acquired from, for example, equation (1) since a transfer function of a system which performs proportional action after a Laplace transform is Kpl (proportional gain) and a transfer function of a system which performs integral action is 1/S (S: Laplace operator).
(Equation Removed)
where:
Kpl is a proportional gain; and
Til is an integration time. Equation (1) is an example which realizes the tension control means 152 (see FIG. 1) with a proportional and integral control.
Thereafter, speed synchronize means 153 shown in FIG 1 executes a speed synchronize process so-called a successive.
When a work roll gap which is a distance between the work rolls 104 and a speed of the work rolls 104 are changed at the stand 120 which is present at the delivery side of the stand 101, the speed synchronize process is for compensating a speed variation AV2 of the strip 103 corresponding to such change at the entry-side stand 101.
If a circumferential speed of the work rolls 104 of the stand 101 is A, then a speed of the strip 103 at the entry side, i.e., an upstream side of the stand 101 (a speed of the strip 103 at the left of the stand 101 in FIG 1) can be expressed as (l-b)A, where b is so-called a backward slip.
Meanwhile, a speed of the strip 103 at the delivery side, i.e., at the downstream side of the stand 101 (a speed of the strip 103 at the right of the stand 101 in FIG 1) can be expressed as (l+f)A, where f is a forward slip.
b (backward slip) and f (forward slip) can be derived from a deformation model of the strip just in rolling based on equilibrium of force.
If a strip thickness of the strip 103 at the entry side, i.e., at the upstream side of the stand 101 (left of the stand 101 in FIG 1) is tl and a strip thickness of the strip 103 at the delivery side, i.e., at the downstream side of the stand 101 (right of the stand 101 in FIG 1) is t2, then a continuous equation (l-b)Atl = (l+f)-A-t2 is satisfied since the strip 103 is continuous.
Regarding a speed of the strip 103, a strip speed meter is attached at the delivery side of a final stand, and a strip speed at the delivery side of the final stand is measured and an intra-stand strip speed is presumed by combining a relationship in the foregoing equation with a presumption using following equation (2) and f (forward slip), b (backward slip) of the work rolls 104 based on a measured value by the strip speed meter. Note that a strip speed meter may be provided at each portion of a rolling line, and all values measured by all strip speed meters may be used as a strip speed at each portion of the rolling line.
Speeds of the strip 103 at the front of the work rolls 104 of the stand 101 and at the back thereof have a relationship V2/(l+f) = Vl/(l-b), where VI is a strip speed at the entry side of the stand 101 (left of the stand 101 in FIG. 1) and V2 is a strip speed at the delivery side of the stand 101 (right of the stand 101 in FIG 1).
When both sides of this equation is differentiated with respect to a time, a change AV2 of V2 when VI is changed by AVI can be expressed as follow if it is linearized around a control point of a speed (velocity) of the strip 103, i.e., around the entry side and the delivery side of the stand 101.
(Equation Removed)
Accordingly, a speed variation AV2 of a speed of the strip 103 at the delivery side, i.e., at the downstream side of the stand 101 (a speed of the strip 103 at the right of the stand 101 in FIG 1) which must be compensated can be expressed as equation (2).
(Equation Removed)
where:
VI is a speed change at the entry side of the stand; and
V2 is a speed change at the delivery side of the stand.
As shown in FIG 1, a rotation speed input V* is input into the speed control means 154 from the tension control means 152 and a speed variation AV2 is input into the speed control means 154 from the speed synchronize means 153. The speed control means 154 then calculates a current instruction (torque instruction) Cl for driving the drive device 109 through an operation of V* + V2.
A current instruction (torque instruction) Cl can be acquired from, for example, equation (3) since a transfer function of a system which performs proportional action after Laplace transform is Kp2 (proportional gain) and a transfer function of a system which performs integral action is 1/S (S: Laplace operator).

(Equation Removed)
where:
Kp2 is a proportional gain; and
TI2 is an integration time. Equation (3) is an example where the speed control means is realized with a proportional and integral control.
FIG. 3 is a diagram showing a process executed by the loading torque observing means 155.
In a step S301 in FIG. 3, the loading torque observing means 155 (see FIG. 1) acquires
an actual value of forward tension tf (measured by the tension meter 113 shown in FIG. 1), an actual value of backward tension tb (measured by the tension meter 132 shown in FIG 1) and an actual value of a rolling load P (P(x)), which are stored in the actual data gathering means 160, from the actual data gathering means 160.
In a step S302 in FIG. 3, a loading torque El applied to one of the work rolls 104 of the stand 101 in total torque of the drive device 109 is estimated as follow.
FIG. 4 shows an example where the strip 103 is rolled by the work rolls 104.
As shown in FIG 4, the strip 103 moves from left to right (a direction of an arrow all in FIG 4). P is a rolling load and P(x) is a rolling load per unit length of the strip 103 at a portion x.
When P(x) is integrated with respect to x, it matches P which is a total rolling load. Moreover, R is a radius of a work roll 104.
At this time, it is known that a loading torque El applied to one of the work rolls 104 can be acquired from following equation (4) (see "Theory and Practice of Strip Rolling", The Iron and Steel Institute of Japan, equation (2.6) in page 14 and equation (2.101) in page 20).
(Equation Removed)
where R' is a flattened roll radius (a radius of a work roll 104 which is deformed in rolling and shortened).
The loading torque observing means 155 estimates a loading torque El by computing equation (4). Eventually, a value acquired by adding a loading torque El computed by the loading torque observing means 155 and a current instruction (torque instruction) Cl computed by the speed control means 154 is output as a current instruction to the drive device 109 (see FIG 1).
Next, an explanation will be given of the looper control system 150B of the tension
control device 150 shown in FIG 1.
FIG. 5 is a diagram showing a configuration of looper-height-instruction generating means 156.
The looper-height-instruction generating means 156 shown in FIG 5 has looper-height-instruction storing means 502 which stores an appropriate looper height instruction 0* determined beforehand correspondingly to a length L of the strip 103 (see FIG 1) which passes through the looper 110 and looper-height-instruction determining means 501 which determines and outputs a looper height (looper height instruction *) based on > information stored in the looper-height-instruction storing means 502.
As shown in FIG. 5, the looper-height-instruction storing means 502 stores data 503 on a looper height instruction 0* that is in a process in which a height of the looper arm 112 increases relative to a leading end of the strip 103 and the looper 110 contacts the strip 103, data 504 on a constant looper height instruction 0* that is in a process in which the looper 110 supports the strip 103 and the strip 103 is fed, and data 505 on a looper height instruction * that is in a process in which a looper height is decreased in the vicinity of a rear end of the strip 103 to cause the looper 110 not to contact the strip 103, which correspond to a pass length L of the strip 103.
Note that the looper 110 contacts the conveyed strip 103 after the strip 103 is sandwiched between the work rolls 104 of the stand 101 and the work rolls 104 of the stand 120, and lifts up and supports the strip 103 (see FIG. 1).
The pass length L of the strip 103 is a distance from a portion of the strip 103 supported by the supporting member 112a of the looper arm 112 in the looper 110 to a leading end of the strip 103.
Accordingly, like the looper-height-instruction storing means 502 shown in FIG 5, a magnitude of the looper height instruction 0* changes in accordance with passing of the strip
103.
The looper-height-instruction determining means 501 acquires a signal representing a pass length L of the strip 103 from the actual data gathering means 160 (see FIG 1), refers to the looper-height-instruction storing means 502 and extracts a looper height instruction 0*. The looper-height-instruction determining means 501 outputs the extracted * as a looper height instruction. Note that data on a pass length L of the strip 103 is acquired by detecting a number of rotation (a rotation speed) or the like of the work rolls 104 which convey the strip 103 and stored in the actual data gathering means 160.
A difference A0 between the looper height instruction 0* and a detected value of a looper height 0 detected by the height meter 114 (see FIG. 1) and stored in the actual data gathering means 160 is input into the looper height control means 157 shown in FIG. 1.
The looper height control means 157 calculates a current instruction (torque instruction) C2 for driving the looper drive device 108 (see FIG 1) from .
Like the foregoing V* and Cl, C2 can be acquired from equation (5).
where:
Kp3 is a proportional gain;
TI3 is an integration time; and
S is a Laplace operator. Equation (5) is an example where the looper height control means 157 is realized with a proportional and integral control.
Next, an explanation will be given of a process of the looper supporting torque estimating means 158 shown in FIG. 1 with reference to FIG. 6. FIG 6 is a diagram showing
a process of the looper supporting torque estimating means 158.
In a step S601 shown in FIG. 6, the looper supporting torque estimating means 158 (see FIG. 1) acquires an actual value of forward tension tf detected by the tension meter 113 (see FIG. 1) and stored in the actual data gathering means 160 and an actual value of a looper height 0 detected by the height meter 114 (see FIG. 1) and stored in the actual data gathering means 160 from the actual data gathering means 160.
In a step S602 in FIG. 6, the looper supporting torque estimating means 158 estimates a looper supporting torque E2 which is a value corresponding to a loading torque for supporting the looper 110 in a total torque of the looper drive device 108 as follow.
FIG. 7 shows an example where the strip 103 being rolled by the stand 101 and the stand 120 is supported by the looper arm 112. Note that FIG. 7 shows a case where the strip 103 is supported by the supporting member 112a of the looper arm 112 at an intermediate position between the stand 101 and the stand 120.
As shown in FIG 7, the strip 103 moves in a direction of an arrow al 1 (from left to right in FIG. 6) while being supported by the looper arm 112, and is rolled by the stand 101 and the stand 120.
In FIG 7, La is a length of the looper arm 112, 0 is a looper height (an angle of the looper arm 112 relative to the horizontal plane) and  is an angle of the strip 103 relative to the horizontal plane.
At this time, it is known that a looper supporting torque E2 for causing the looper arm 112 to maintain an angle 9 (looper angle 0) relative to the horizontal plane can be acquired from equation (6).
(Equation Removed)
where D is a speed friction coefficient with respect to a change in angle of a looper.
Here, Kl(0)-tf is a supporting torque of the looper arm 112 generated by tension of the
strip 103, K2() is a supporting torque of the looper arm 112 generated by supporting a weight of the strip 103, K3() is a supporting torque of the looper arm 112 generated by an own weight of the looper arm 112 and D(d6/dt) is a speed friction torque with respect to a change in angle of the looper. All of those are functions with respect to a looper angle 9, and a value of a looper supporting torque E2 changes depending on a looper angle .
Since loads due to tension tf are generated at both sides of the looper arm 112, K1(0) of a supporting torque generated by tension tf of the strip 103 in the looper supporting torque E2 can be expressed as 2 x tfhbsinp, where h is a thickness of the strip 103, b is a width of the strip 103 and tf is tension per unit area of a cross section of the strip 103, and an arm length of the looper arm 112 around a supporting point can be expressed as Lacos so that Kl() of a supporting torque Kl(9)tf generated by tension tf of the strip 103 can be expressed as following equation (7).
Kl() = 2hbLa-cos sin (7)
On the other hand, K2() in the looper supporting torque E2 acquired from equation (6), i.e., a supporting torque of the looper arm 112 generated by supporting a weight of the strip 103 can be set as follow.
As shown in FIG 7, if a density of the strip 103 is p, a gravitational acceleration is g and a horizontal direction distance of the strip 103 between a contact point with the work rolls 104 of the stand 101 and a contact point with the supporting member 112a of the looper arm 112 is 1, a weight of the strip 103 from the contact point with the work rolls 104 of the stand 101 to the contact point with the supporting member 112a of the looper arm 112 can be expressed as phbg(l/cosP) and a weight of the strip 103 from a contact point with the work rolls 104 of the stand 120 to the contact point with the supporting member 112a of the looper arm 112 can be likewise expressed as phbg-(l/cos).
Since an arm length of the looper arm 112 around a supporting point is Lacos, a supporting torque K2() of the looper arm 112 generated by supporting a weight of the strip
103 can be expressed as following equation (7).
(Equation Removed)
Moreover, a supporting torque K3() of the looper arm 112 generated by an own weight of the looper arm 112 in the looper supporting torque E2 acquired from equation (6) can be expressed as following equation (9) with reference to FIG 7
(Equation Removed)
where:
ml is a mass of the looper arm 112;
g is a gravitational acceleration; and
rl is a distance from a supporting point of the looper arm 112 to a position of the center of gravity of the looper arm 112.
As explained above, using E2 estimated by the looper supporting torque estimating means 158, a value acquired by adding E2 to a current instruction (torque instruction) C2 acquired by the looper height control means 157 is output as a current instruction to the looper drive device 108.
Unlike FIG. 7, when the strip 103 is supported by the supporting member 112a of the looper arm 112 at other than the intermediate portion between the stand 101 and the stand 120, a looper supporting torque E2 can be acquired in consideration of an angle of the strip 103 from a horizontal plane of the stand 101, 120 and a distance of the strip 103 from a contact point with the work rolls 104 of the stand 101 to a portion supported by the supporting member 112a of the looper arm 112.
Through the foregoing computation, the drive device 109 and the looper drive device 108 both shown in FIG. 1 operate together while eliminating an interactive system between a speed of the strip 103 and looper height at the time of rolling.
The explanation has been given while exemplifying one stand 101 and the looper 110 in
the first embodiment. However, the present invention can be easily applied to a tandem mill having successive plural stands 101 in a multi-stage manner by preparing the tension control system 150Aand the looper control system 150B which execute the foregoing processes for each stand and each looper. «Second Embodiment»
Next, an explanation will be given of a control system 2S according to a second embodiment of the present invention.
FIG. 8 is a diagram showing a structure of the control system 2S according to the second embodiment.
As shown in FIG 8, the control system 2S of the second embodiment uses an instruction value tf of forward tension acquired from tension target value storing means 251 instead of an actual value acquired from actual data gathering means 260, regarding forward tension tf of a strip 203 conveyed from a stand 201 among all input into a loading torque observing means 255.
The other structures are the same as those of the first embodiment, and the same components will be denoted by reference numerals in the 200s and detailed explanation thereof will be omitted.
In a hot rolling device 200 of the control system 2S shown in FIG 8, the strip 203 is conveyed in a direction of an arrow 21 and is subjected to hot rolling by stands 201, 220.
FIG. 9 is a diagram showing a flow of a process executed by the loading torque observing means 255 according to the second embodiment of the present invention.
In a step S901 in FIG. 9, the loading torque observing means 255 (see FIG 8) acquires a forward tension instruction value tf from the tension target value storing means 251.
In a step S902 in FIG 9, the loading torque observing means 255 (see FIG 8) acquires an actual value of backward tension tb and an actual value of a rolling load P or an actual value of a rolling load P(x) per unit length of the strip 203 at a portion x from the actual data
gathering means 260.
In a step S903 in FIG. 9, a loading torque El is calculated through equation (1) and is output.
According to the foregoing structure, the loading torque observing means 255 uses the forward tension instruction value tf as forward tension tf instead of an actual value thereof so that an observing accuracy for a loading torque is lowered by what corresponds to a difference between an actual value in the hot rolling device 200 and the instruction value tf". At the same time, because forward tension tf is fixed by the forward tension instruction value tf* instead of an actual value, a loading torque estimating result (a loading torque El) becomes independent from a change in forward tension in the hot rolling device 200, and a rotation of work rolls 204 can be controlled by a drive device 209 with a current instruction independent from a change in an actual value of forward tension tf, thereby suppressing any vibration of the conveyed strip 203.
Accordingly, there is an advantage that a conveying of the strip at the time of rolling in the hot rolling device 200 can be stabilized. «SUMMARY»
According to the present invention, it is focused on that an interaction between a tension control through tension and a looper height control become obvious in a torque change, and loading torque observing means which estimates a load of a drive device and looper supporting torque estimating means which estimates a load of a looper drive device are employed. A loading torque estimating result is subjected to a feed-forward addition to a current instruction (torque instruction) to the drive device, and a looper supporting torque estimating result is subjected to feed-forward addition to a current instruction (torque instruction) to the looper drive device.
That is, in a looper/tension control system, a tension control is controlled by a speed control by a main drive which conveys a rolling target, while at the same time, a looper height
is controlled by a looper height control by employing two one-input/one-output systems.
In addition, in order to cause a tension control of a strip between stands and a looper height control to be mutually non-interactive, the loading torque observing means which estimates a loading torque of the main drive that conveys the rolling target and the looper supporting torque estimating means which estimates a loading torque of a looper are provided.
A value acquired by adding an estimated loading torque to a speed control value of the main drive is taken as a new speed control value of the main drive, a value acquired by adding an estimated looper supporting torque to a looper height control value is taken as a new looper height control value, and both new values are output to the control-target hot rolling device.
The loading torque observing means in the tension control system estimates a loading torque to be applied to the main drive which conveys a rolling target with forward tension when the rolling target is ejected from a stand, backward tension when the rolling target is entered into the stand and a rolling load at that stand being taken as input.
The looper supporting torque estimating means in the looper height control system calculates a torque which is necessary for the looper to support the strip through a computation using a looper height and strip tension.
A change in tension which affects a looper height due to a speed control for the main drive conveying the rolling target can be detected as a change in a load when the looper supports the strip.
Likewise, a change in tension affecting a speed of the main drive when a looper height is changed can be detected as a change in a torque of the main drive.
The loading torque observing means and the looper supporting torque estimating means are provided in focusing on such characteristics. As the loading torque observing means detects a change in tension as a change in a loading torque when a looper height is controlled
and performs feed-forward compensation on a speed control instruction for the main drive with a manipulated variable in order to cancel such a change, an effect thereof is made non-interactive.
Likewise, the looper supporting torque estimating means detects a change in tension due to a speed control for the main drive which conveys a rolling target as a change in a loading torque supporting a strip and performs feed-forward compensation on a looper height control instruction with a manipulated variable in order to cancel such a change, thereby making an effect thereof non-interactive.
Thus, tension and a looper height can be both stably controlled while in consideration of an interaction between a tension control and a looper height control through tension.
Therefore, a tension control for a material at a stand is stabilized in hot rolling, and a stability of a material at the time of rolling and feeding thereof can be improved, resulting in achievement of a highly precise material thickness.
Moreover, as tension of the material at the time of rolling is stabilized, width shrinkage deviation of the material due to a change in tension can be suppressed so that a strip width precision can be improved.
INDUSTRIAL APPLICABILITY
The present invention can be widely used for a looper control of a hot rolling tandem mill having a looper between finishing stands, such as a conventional mill or a mini mill.

WHAT IS CLAIMED IS:
1. A tension control device for hot rolling which controls a hot rolling mill having plural rolling stands and a looper between the plural rolling stands and which controls tension of a rolling target like a strip to a desired value, the rolling target being rolled continuously by work rolls of the individual rolling stands, the tension control device comprising:
tension control unit for controlling the tension of the rolling target to a desired value by controlling a work roll rotation speed of each rolling stand;
speed control unit for calculating, from an output of the tension control unit, a speed instruction for a drive device which drives the work rolls, the speed instruction being for controlling the work roll rotation speed;
loading torque observing unit for estimating a loading torque of the drive device by acquiring an actual value of backward tension which is tension of the rolling target entering into the rolling stand, an actual value of forward tension which is tension of the rolling target ejected from the rolling stand, and an actual value of a rolling load of the rolling stand from the hot rolling mill;
looper height control unit for outputting a control instruction, which is a value computed by using an output of a speed instruction calculated by the speed control unit and an output of the loading torque estimated by the loading torque observing unit, to the drive device, and for calculating a height instruction for a looper drive device which controls a height of the looper; and
looper supporting torque estimating unit for acquiring an actual value of the forward tension and an actual value of a height of the looper from the hot rolling mill, and for estimating a torque necessary for the looper to support the rolling target,
wherein a control instruction, which is a value acquired by computing an output that is a height instruction calculated by the looper height control unit and an output that is a torque
estimated by the looper supporting torque estimating unit, is output to the looper drive device.
2. A tension control device for hot rolling which controls a hot rolling mill having plural rolling stands and a looper between the plural rolling stands and which controls tension of a rolling target like a strip to a desired value, the rolling target being rolled continuously by work rolls of the individual rolling stands, the tension control device comprising:
tension control unit for controlling the tension of the rolling target to a desired value by controlling a work roll rotation speed of each rolling stand;
speed control unit for calculating, from an output of the tension control unit, a speed instruction for a drive device which drives the work rolls, the speed instruction being for controlling the work roll rotation speed;
loading torque observing unit for estimating a loading torque of the drive device using a target value of forward tension which is tension of the rolling target ejected from the rolling stand by acquiring an actual value of backward tension which is tension of the rolling target i entering into the rolling stand and an actual value of a rolling load of the rolling stand from the hot rolling mill;
looper height control unit for outputting a control instruction, which is a value computed by using an output of a speed instruction calculated by the speed control unit and an output of the loading torque estimated by the loading torque observing unit, to the drive device, and for calculating a height instruction for a looper drive device which controls a height of the looper; and
looper supporting torque estimating unit for acquiring an actual value of the forward tension and an actual value of a height of the looper from the hot rolling mill, and for estimating a torque necessary for the looper to support the rolling target,
wherein a control instruction, which is a value acquired by computing an output that is a height instruction calculated by the looper height control unit and an output that is a torque
estimated by the looper supporting torque estimating unit, is output to the looper drive device.
3. A tension control method for hot rolling which comprises plural rolling stands and a looper provided between the rolling stands to support a rolling target like a strip to stabilize a rolling process by a supporting height, and which controls tension of the rolling target to a desired value, the rolling target being rolled continuously by work rolls of individual rolling stands, the method comprising steps of:
calculating a rotation speed of a drive device which drives the work rolls in order to control the tension of the rolling target to a desired value;
calculating a speed instruction value for the drive device corresponding to the rotation speed of the drive device;
estimating a loading torque of the drive device which drives the work rolls by acquiring an actual value of backward tension which is tension of the rolling target entering into the rolling stand, an actual value of forward tension which is tension of the rolling target ejected from the rolling stand and an actual value of a rolling load of the rolling stand;
outputting a control instruction which is a value acquired by computing a speed instruction value for the drive device and a loading torque of the drive device to the drive device;
calculating a height instruction value for a looper drive device which controls a height of the looper to a desired value;
estimating a supporting torque necessary for the looper drive device to support the rolling target by acquiring an actual value of the forward tension and an actual value of a height of the looper; and
outputting a control instruction which is a value acquired by computing a supporting torque for the looper drive device and a height instruction value for the looper drive device to the looper drive device.
4. A tension control method for hot rolling which comprises plural rolling stands and a looper provided between the rolling stands to support a rolling target like a strip to stabilize a rolling process by a supporting height, and which controls tension of the rolling target to a desired value, the rolling target being rolled continuously by work rolls of individual rolling stands, the method comprising steps of:
calculating a rotation speed of a drive device which drives the work rolls in order to control the tension of the rolling target to a desired value;
calculating a speed instruction value for the drive device corresponding to the rotation speed of the drive device;
estimating a loading torque of the drive device which drives the work rolls using a target value of forward tension which is tension of the rolling target ejected from the rolling stand by acquiring an actual value of backward tension which is tension of the rolling target entering into the rolling stand and an actual value of a rolling load of the rolling stand;
outputting a control instruction which is a value acquired by computing a speed instruction value for the drive device and a loading torque of the drive device to the drive device;
calculating a height instruction value for a looper drive device which controls a height of the looper to a desired value;
estimating a supporting torque necessary for the looper drive device to support the rolling target by acquiring an actual value of the forward tension and an actual value of a height of the looper; and
outputting a control instruction which is a value acquired by computing a supporting torque for the looper drive device and a height instruction value for the looper drive device to the looper drive device.